1. Field of the Invention
The present invention relates generally to a new and improved process and apparatus for randomly selecting any preselected number of samples of an item from any preselected batch or population number for that item. The item being monitored may be any item which is being produced in quantity, the level of quality of which it is desirable to inspect from time to time.
For purposes of the disclosure herein, the term "batch" or "population" is taken to mean the group of all the items that fit a particular description, for example, a production run; the term "sample" is taken to mean a number of objects chosen for a given batch or population as representative of the entire group; and "random sample" is a sample in which every item in the batch or population has an equal chance of being chosen for the sample.
2. Description of the Prior Art
It is customary in many industries utilizing mass production techniques to remove, at intervals, items being produced as they advance along the assembly line. These items are then examined to determine their fitness for sale and consumption. In the ideal world, each item would be examined. However, such 100 percent examination is a practical or commercial impossibility since the time and, therefore, cost involved would not permit it. Furthermore, it is not necessary to perform such a total examination in any event, since, statistically, it is very likely that if a proper sampling is taken, any problems present will appear. And if a problem with the production item appears in quantities that are greater than a permissible level, that is a clear indication that some action must be taken with the entire production run in order to alleviate the problem.
Such sampling is of particular importance in the food and beverage processing industries to assure that items intended for human consumption are fit for such consumption. However, various sampling techniques have been used in virtually every industry in which relatively large numbers of items are produced and in which it would be impractical or impossible to inspect every single item.
However, not only is it necessary that a sampling of items be made in order to determine the quality of the vast majority of the items in the entire batch or population from which the inspection is taken. Indeed, it is necessary that the sampling be random in order for it to be effective. It will be appreciated that machinery operates in a repetitive fashion and that while this is a desirable characteristic for many functions, it is an undesirable characteristic when the goal is to obtain randomness of operation. Specifically, it is possible that a selection of items at uniformly spaced intervals during a production run could establish a pattern which would closely match a pattern in the population of the items such that an accurate representation of the finished product is not obtained. For example, most filling and packaging systems operate on a fixed scale basis such that a uniformly spaced selection of sample items could result in obtaining successive sample items which were filled by the same station of a filling machine or closed by the same station of a sealing machine. By so dwelling on one aspect of the production run, a problem which might actually exist at some other station of the machinery might be overlooked.
The most pertinent prior art known to the inventor will now be discussed. The U.S. patent to Hrabak, U.S. Pat. No. 3,151,237 issued Sept. 29, 1964, is representative of that class of inventions in the prior art which serves to glean an amount of a variable for controlling the quality of that specific variable. The patent is not concerned with random number selection, but discloses a statistical quality control system for determining the statistical distribution of certain quality characteristics of an article of manufacture.
The U.S. patent to Wallace et al., U.S. Pat. No. 4,187,545 issued Feb. 5, 1980, is representative of that class of prior art inventions which serve to compare an article of manufacture being produced with an established one. If there is a problem, that problem is corrected or the item causing the problem is ejected. In the Wallace patent, apparatus is disclosed for determining the orientation of articles advancing along a conveyor, correcting them if they are not properly oriented or ejecting them for another attempt. As with the Hrabak patent, there is no consideration or discussion in the Wallace patent of random number selection.
The U.S. patent to Weaver, U.S. Pat. No. 3,944,051 issued Mar. 16, 1976 is the prior art known to the inventor which is closest in concept to the invention. Weaver utilizes a pair of counters which operate in conjunction with a switching mechanism to achieve some degree of randomness. However, unlike the system employed in the present invention, Weaver seeks to achieve a result in which the random selection is spread evenly across the entire production run. That is, according to the system of Weaver, only one sample is chosen out of a predetermined batch size which will result in a preselected whole number percentage at the end of a production run. On each occasion that the first counter recycles, for example, after the passage of every 50 or 100 articles of the production run, a new batch is begun. Although the Weaver system does achieve a certain level of randomness, it does not achieve that degree of randomness which modern industry, particularly the food processing industry, considers necessary in order to provide the quality of product properly demanded by today's consumer.
With proper deference being given to the aforesaid patents, each of which, on its face, discloses an advance in the state-of-the-art as of the date when each respective patent was granted, nonetheless, the present invention is deemed to be a considerable improvement over such known devices. Indeed, it was with recognition of the need and the state of the prior art that the present invention was conceived and has now been reduced to practice.